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Marc A. Lehmann


Coro - coroutine process abstraction


 use Coro;

 async {
    # some asynchronous thread of execution

 # alternatively create an async process like this:

 sub some_func : Coro {
    # some more async code



This module collection manages coroutines. Coroutines are similar to Threads but don't run in parallel.

This module is still experimental, see the BUGS section below.

In this module, coroutines are defined as "callchain + lexical variables + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own callchain, it's own set of lexicals and it's own set of perl's most important global variables.


This coroutine represents the main program.

$current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value is $main (of course).


The coroutine to switch to when no other coroutine is running. The default implementation prints "FATAL: deadlock detected" and exits.


Static methods are actually functions that operate on the current process only.

async { ... } [@args...]

Create a new asynchronous process and return it's process object (usually unused). When the sub returns the new process is automatically terminated.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

The coderef you submit MUST NOT be a closure that refers to variables in an outer scope. This does NOT work. Pass arguments into it instead.


Calls the scheduler. Please note that the current process will not be put into the ready queue, so calling this function usually means you will never be called again.


"Cede" to other processes. This function puts the current process into the ready queue and calls schedule, which has the effect of giving up the current "timeslice" to other coroutines of the same or higher priority.


Terminates the current process.

Future versions of this function will allow result arguments.

# dynamic methods


These are the methods you can call on process objects.

new Coro \&sub [, @args...]

Create a new process and return it. When the sub returns the process automatically terminates. To start the process you must first put it into the ready queue by calling the ready method.

The coderef you submit MUST NOT be a closure that refers to variables in an outer scope. This does NOT work. Pass arguments into it instead.


Put the current process into the ready queue.


Like terminate, but terminates the specified process instead.

$oldprio = $process->prio($newprio)

Sets the priority of the process. Higher priority processes get run before lower priority processes. Priorities are smalled signed integer (currently -4 .. +3), that you can refer to using PRIO_xxx constants (use the import tag :prio to get then):

       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH

The idle coroutine ($Coro::idle) always has a lower priority than any existing coroutine.

Changing the priority of the current process will take effect immediately, but changing the priority of processes in the ready queue (but not running) will only take effect after the next schedule (of that process). This is a bug that will be fixed in some future version.

$newprio = $process->nice($change)

Similar to prio, but subtract the given value from the priority (i.e. higher values mean lower priority, just as in unix).


 - could be faster, especially when the core would introduce special
   support for coroutines (like it does for threads).
 - there is still a memleak on coroutine termination that I could not
   identify. Could be as small as a single SV.
 - this module is not well-tested.
 - if variables or arguments "disappear" (become undef) or become
   corrupted please contact the author so he cen iron out the
   remaining bugs.
 - this module is not thread-safe. You must only ever use this module from
   the same thread (this requirement might be loosened in the future to
   allow per-thread schedulers, but Coro::State does not yet allow this).


Coro::Channel, Coro::Cont, Coro::Specific, Coro::Semaphore, Coro::Signal, Coro::State, Coro::Event, Coro::RWLock, Coro::Handle, Coro::Socket.


 Marc Lehmann <pcg@goof.com>

2 POD Errors

The following errors were encountered while parsing the POD:

Around line 80:

'=item' outside of any '=over'

Around line 128:

You forgot a '=back' before '=head2'